“Journals that use a funding model that does not charge readers or their institutions for access ... [permitting] any users to read, download, copy, distribute, print, search, or link to the full texts of these articles." (DOAJ)
Gold OA – Journals with immediate, free access to all of its articles on publisher’s website (e.g., PLoS ONE, Biogeosciences).
Delayed OA – Journals with free access to articles after a certain embargo period (typically 6-12 months); newer articles require subscription (e.g., PNAS, Astrophysical Journal).
Hybrid OA – Journals with free access to only certain articles, based on author paying an optional open access processing fee, variously known as Author Choice, Open Choice, Author Select, etc. (e.g., Physical Review, JGR).
Green OA (Self-Archiving) – Journals that permit authors to post versions of their articles for free access on personal/institutional websites, in institutional repositories (e.g., DSpace@MIT), or in disciplinary repositories (e.g., arXiv, PubMed Central) at the time of publication. Typically used for postprints (final draft post-refereeing), but sometimes for preprints (manuscript pre-refereeing) or actual publisher PDFs. Policies may be tied to OA mandates from funding agencies like NIH, HHMI, Wellcome Trust.
7000+ OA journals are currently published and several hundred new ones are being launched each year.
530 scholarly societies currently publish 616 full OA journals. 78% are in science-technology-medicine. (Suber, 2011).
20% of peer-reviewed literature published in 2008 is openly available on the web: 8.5% on publisher’s sites, 11.9% as full-text versions in repositories and on author/department websites. (Björk et al., 2010).
Earth sciences has highest overall OA share (33%); chemistry the lowest share (19%). (Björk et al., 2010).
89% of researchers say OA is beneficial to scholarship and 53% have published at least one OA article; but overall only 10% of papers are published in OA journals. Main reasons cited: lack of funding for publication fees (40%) and lack of high-quality OA journals in their field (30%). (Survey of 50,000 researchers in EU-sponsored “Study of Open Access Publishing” (SOAP), 2009-2011).